AXPZ20 KNHC 280238
TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 UTC SAT MAY 28 2016
Tropical weather discussion for the eastern Pacific Ocean from the Equator to 32N, east of 140W. The following information is based on satellite imagery, weather observations, radar, and meteorological analysis.
Based on 0000 UTC surface analysis and satellite imagery through 0215 UTC.
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...
The monsoon trough axis extends from 10N84W to 08N92W to 12N109W to low pressure near 10N122W 1008 mb to 06N131W. ITCZ axis extends from 06N131W to 06N140W. Scattered moderate to isolated strong convection is within 120 nm s of the axis between 88W and 92W...and within 120 nm of the axis between 92W and 98W. Scattered moderate convection is within 180 nm s of the axis between 98W and 104W...and within 60 nm of the axis between 124W and 126W.
High pressure north of the area centered near 38N138W extends a ridge axis southeastward to 32N135W to 24N127W to near 18N112W. High pressure covers the area north of 15N west 118W. This subtropical ridge in combination with the convergence zone south of 11N continues to influence most of the area W of 110W. Ascat data from Friday afternoon indicated fresh north to northeast winds north of the ITCZ to near 22N and west of about 118W.
Global models are persistent in depicting a broad, fairly weak area of low pressure across the central waters in the vicinity of 10N122W. The models suggest some development of the low pressure beginning on Saturday as the low remains in a col region between two anticyclones...one centered near 12N135W
...and the other near 15N106W. It is expected that a tight pressure gradient will develop between the low and the aforementioned ridge to its north tonight into Saturday. This gradient will then lead to fresh to strong northeast winds in the NW quadrant of the low with seas building to 8 to 9 feet by early Sun morning. The low is forecast by consensus of the model guidance to meander near the general vicinity of 121W-122W Saturday then begin to lift to the northeast late Saturday into Sunday while changing little in intensity. A very active eastern segment of the monsoon trough may spawn weak low pressure near 90W on Saturday.
Elsewhere, gale force northerly winds north of the area near the California coast are expected to produce an area of N swell that will extend south of 32N beginning late tonight and affect the north-central waters N of about 28N between 122W and 129W through Sunday. Cross-equatorial south to southwest swell with seas of 8 feet is forecast to arrive into a portion of the far southern waters early on Saturday...namely south of 05N between 113W and 120W. By late Saturday afternoon, the swell is forecast to expand west and northwest in coverage to be located south of 05N between 114W and 120W, and south of 03N between 120W and 129W. The swell area is forecast to extend as far southeast as 03.4S95W by Sunday afternoon, and west to 134W south of 03N with seas at that time expected to build to 9 feet. Otherwise, rather tranquil marine conditions are expected to prevail across the remainder of the forecast area through Sun.